1. Field of the Invention
The present invention relates to an improved gas filtering apparatus and method. In particular the present invention relates to an apparatus and method adapted for cleaning air of small, micron sized particles.
2. Prior Art
The prior art is concerned with conservation of energy used to heat a gas, particularly air, used in a confined work space where small particles are generated. Under manufacturing conditions, air can accumulate very fine micron sized particles which are a health hazard and which can create a fire hazard. In many plants, in the winter, the particle laden, heated air is vented to the atmosphere and fresh air is heated from outside ambient temperatures for use in the building. In the summer, the reverse is true and cooled air is vented. This process is a waste of energy, since the particle laden gas or air can be cleansed and recycled.
U.S. Pat. No. 1,965,717 to Wechsberg describes a dust filter device as does Canadian Pat. No. 1,072,890 to Muermans. In these devices the filter medium is unsupported and the filters are concerned with dust sized particles (50 microns and above). The air flow is parallel to the surface of the filter medium.
The prior art is faced with the problem of providing appropriate filter medium and filtering apparatus which allows for filtering of micron sized particles particularly for welding smoke and oil mist. The problem is to remove micron sized particles such as smoke or oil mist. Generally the prior art has used apparatus wherein gas flow towards the filter medium is perpendicular to the general plane of the medium, tending to drive the particles through the medium. Because of the density of the filter medium a porous support must be used for support of and transfer of the filter medium.
The prior art shows various types of filter media having a sawtoothed configuration. In all of this prior art where a porous support is used the gas flow is directed towards the projections defining the sawtoothed configuration with the gas flow perpendicular to the general plane defined by the filter medium. I have found that the particles in the gas tend to be driven directly through the filter medium even with this configuration. Also this gas flow creates turbulence at the filter medium surface and tends to dislodge particles embedded in the medium.
U.S. Pat. No. 2,016,991 to Dollinger, shows the use of moveable screen belts 7a supporting a filter medium in a sinuous path where the gas flow p is directed towards the projections and the general plane of the filter medium. The filter medium is slightly wider than the width of the casing 4 which forms a seal with the walls of the casing.
U.S. Pat. No. 1,982,639 to Christofferson shows a device wherein non-moveable screens 31 position the filter media B during filtration. Automatic feed means is provided for advancement of the filter media. The gas flow is directed towards the projections and the general plane of filter medium.
U.S. Pat. No. 2,076,305 to Strindberg shows a similar type of device to that described by Dollinger without the moveable screen.
U.S. Pat. No. 2,133,931 to Walker et al describes a mechanism for forming a sinuous filter medium whereby wedge shaped clamping rails 28 and 29 on slide plates 14 are moveable to engage the filter media A during filtration. The gas flow is the same as Dollinger.
U.S. Pat. No. 3,019,855 to Engle describes specific means for securing the edges of the filter media 45 and also a means for detecting the difference in pressure in the filter media in order to provide for advancement for the fresh media. The gas flow is the same as the earlier patents.
U.S. Pat. No. 3,045,410 to Floyd shows a roll type device wherein the rolls 12 are in contact with the filter media 19. The gas flow is conventional.
U.S. Pat. No. 3,406,503 also to Floyd shows a mechanism for the edge support of the filter media. The gas flow is conventional.
U.S. Pat. No. 3,438,588 to Steinholtz et al shows a device wherein the filter media 1 is continuously fed from a roller 2 in a zigzag, sawtoothed or sinuous path. The gas flow is conventional.
U.S. Pat. No. 3,552,099 to Floyd shows a sawtoothed type filter web with a specific form of sealing means for the filter media 30. The gas flow is conventional.
One of the earliest patents is Birkholz, U.S. Pat. No. 1,783,181, wherein a rotary drum supports a moveable filter media. This patent describes the use of automatic means to advance the filter media after it encounters objectionable resistance because of the accumulation of particles. U.S. Pat. No. 3,596,442 to Neumann and U.S. Pat. No. 3,745,748 to Goldfield show improvements on this basic patent. The gas flow is conventional.
There are numerous other patents showing various devices to be used with gas (air) filters or other filter medium configurations, including U.S. Pat. Nos. 2,113,896; 2,881,859; 2,848,064; 2,853,155; 3,020,976; 3,332,215; 3,337,898; 3,350,853; 3,350,854; 3,464,487; 3,467,797; 3,348,366; 3,774,373; 4,229,187; 3,985,528; 4,011,067 and 4,054,521. In all of the prior art devices the flow of the gas is perpendicular to the general plane of the filter. In some an electrostatic charge is created (U.S. Pat. No. 4,229,187) to facilitate the capture of the particles.